Easy to read, write and update with the help of a machine called a computer.

Information on a floppy disk is susceptible to damage from outside magnetic fluctuations (e.g. a power cable).

CD-ROM

For a slightly higher cost, a CD-ROM can store about 440 floppy disks (or between 650MB and 700MB) worth of information, making it suitable for multimedia applications

Requires additional tools (i.e. a computer, CD drive and software) to read
information on a CD-ROM.

Normal everyday magnetic fluctuations will not affect the media or the information stored on CD-ROM.

Only the most intense magnetic fluctuations in certain laboratories could cause the reflective media (if made of aluminium) to heat up and melt.

Information can be accessed with great speed.

The construction of early CD-ROMs had poor quality plastics that can chemically react with the reflective (aluminium) media, and thereby reducing its lifespan for storing information. Nowadays, the plastics have been improved with built-in chemical dyes to prevent this problem. However, the plastics still have one other problem: they are too soft and can scratch easily and this can affect the quality of the information getting through the plastic when it is read by a laser disc player.

If high quality materials and special dyes are used, CD-ROMs can last for 200 years or more.

THE INTERNET

Information can reach an extremely wide audience quickly and easily with
minimal cost.

The content and presentation of many Internet sites is often of a low quality.

The number of computers connected to the Internet is already a massive storehouse of information, far greater than can be stored on a single CD-ROM or book.

It can be difficult to find specific information you want quickly and easily.

Information on the Internet can be modified in a matter of minutes at little
or no cost, allowing people to access the very latest information.

Additional tools are required to access the Internet (i.e. a computer, a
modem, a telephone network and software).

The type of media used to store information on the Internet is not important.

Accessing multimedia-rich information on the Internet tends to be slow due to limited bandwidth in the network.

Tips on looking after your CDs

Contrary to early reports, the surface of compact discs (CDs) are easily damaged by sunlight, heat, dust, humidity and through normal touching with your hands or contact with a hard surface. If a CD is damaged, the most common problem you will discover when using the CD is either (i) a skip in the music; or (ii) there is a permanent file error while reading the data on the CD with a computer.

To protect the CD from scratches, fingerprints, dust particles and smears, do not touch or place it face down on a hard surface the "unlabelled" side of the disk containing the stored data. Handle the disc only by the outer edge. To avoid scratches when using the CD to extract information, use a high-quality CD player to ensure the CD spins consistently in one spot during normal use. When not in use, store the CD inside its protective case and leave it in a dark, dust-free place.

The recommended storage conditions for CDs are:

Temperature: 10°C to 50°C (50°F to 122°F)

Humidity: 10% to 80%

Should the CD become dirty from spots, dust or fingerprints, clean it with a soft lint-free high-quality cloth as used by opticians, working from the centre to the edge. The cloth should be moistened with a quick drying liquid like ethyl alcohol. But never use any harsh solvent like benzine, lacquer thinner, anti-static agents, or LP record cleaners as they will permanently damage the outer plastic surface of your CD.

What if I have valuable data on CD that I wish to use regularly?

For important data you want to store on a CD and use regularly, we recommend that you duplicate the CD. In that way, the original CD can be stored in a safe place for a long time, and the second CD can be used in the normal way. When the CD copy is eventually damaged through "wear-and-tear", make another CD copy from the original CD and continue to use in the usual way.

What if I wish to preserve digital information forever?

There is no single CD that will last forever and so permanently preserve the digital information recorded on it.

The only way to permanently preserve digital information is to (i) make several CD copies of the information and distribute it as widely as possible; and (ii) duplicate the information onto a fresh CD every 10, 25, 50 or 150 years, depending on the quality of the original CD media.

Currently, the coloured dyes now used in the plastics of some CDs (e.g. the Kodak variety and other reputable brands) will help to preserve the plastics and the reflective material inside containing the digital information for up to 200 years when kept at the recommended storage conditions.

What are the better CD-R and CD-RW disks to use?

It will depend on what you intend to use them for. If it is to make regular backup copies of data and replace them within 5 years, all CD-R and CD-RW disks are fine. In which case, you will not need an expensive disk to do the job.

If, on the other hand, you want to preserve information onto CDs for as long as possible, you are better off having the data etched onto a titanium metal disk and protected inside two "scratch-proof" glass wafers and then store the disk inside a tough and durable plastic case. The information should then last for centuries, perhaps thousands of year.

But this is a very expensive option.

If you want to use the available range of cheaper CD-R disks in the marketplace, you would be better off buying one of those disks that use a gold reflective layer together with the plastic component containing the vital phthalocyanine (transparent) dye as required for recording the digital information, such as used on the gold disks from Kodak and other manufacturers. Avoid the blue or green CD-R disks made with a cyanine or azo dye if longevity is required and you want to read the disks properly in all older and newer CD burners and readers.

If both disks are exposed to regular sunlight or UV light, the phthalocyanine-based disks do last longer (up to 100 years) compared to around 50 years for the cyanine-based disks. If stored properly and sealed inside its own protective metallic symmetrical casing, the phthalocyanine-based disks should last over 200 years.

However, the dye formulation used in CD-R disks are changing every year. Currently, Verbatim is one progressive company making CD-R disks. They now claim a new azo formulation for their latest CD-R disks offers much better wear-and-tear to sunlight and will last as long as 120 years.

But just to keep the customers on their toes, each dye will prefer a longer or shorter electromagnetic pulses in the laser signal from a CD burner to record the digital 0's and 1's into microscopic 'pits' and 'lands" (or permanent changes in the reflectivity of the organic dye used inside the polymer (plastic) disk). Unfortunately CD burners are not manufactured to detect different dyes used in the CD-R disks and therefore you could end up buying a CD burner designed to work best on a certain CD-R disk. Although all CD burners should work with all CD-R disks, CD burners will be optimised for either short or long pulses in the laser signal and hence a particular brand of CD-R disks.

If longevity and a good, clean signal etched into the CD-R disk is required, try to go for a CD burner with a short pulse rate. The short pulse rate will also be suitable with phthalocyanine-based disks. Otherwise, stick to the CD burners with a long pulse rate as these would be optimised for cyanine-based disks.

CD-RW disks can be used to store information. The big advantage of CD-RW disks is you now have the ability to re-record digital information up to 1,000 times thereby saving the environment of a thousand CD-R disks ending up in the rubbish tips of the world. The only problem with CD-RW disks is the patterns created on the disk during the burning process are less distinct than in a CD-R and therefore is much harder to read on CD players and DVD drives.

For longevity, you should stick to the CD-R disks.

How much information should I store on a CD-R and CD-RW disk?

Stick to a capacity of less than 650MB per CD-R. There are 703MB CD-R disks you can buy. They simply make the spiralling track of digital information etched onto the disk tighter and more compact, thereby fitting more grooves on. But not all CD players can handle these disks.

And if you are intending to make CD-ROMs from your CD-R disks for replication and commercial distribution, you are best to keep to the 650MB limit for maximum compatibility with any CD-ROM or CD audio player.

Is there a better alternative?

Now that DVDs are becoming the standard in optical storage disks with its 4.7GB capacity and with more and more computers able to burn DVDs just as well as CDs, the option is there to consider storing information on DVDs.

Again the longevity of DVDs is depended on the materials and dyes used to construct the disks. If DVDs are relatively common and easily accessable in your area and can find quality DVD disks, then consider them as the replacement for CDs.